In the maintenance and possibly manufacturing or rework of aircraft propellers it is required that certain damaged protective films be removed and fresh films be applied to refurbish the propellers and return them to use. Such rework or repair may also be required for large turbine blades of wind powered electric generators. Damage to propellers or blades often occurs from normal use such as wear and tear from high speed impact of rain and ice particles or bird strikes to sand and gravel impact. Some aircraft runways may consist of only a “dirt”strip or a sandy beach. As such, debris can become airborn and flow into the propeller or blade wash. Propeller damage may also result from military conflict or simple maintenance accidents.
A conventional example of an aircraft propeller and coating is that of a painted metal propeller. However, more recently developed high efficiency and light weight propellers are constructed of fiberglass or carbon fiber composite substrates rather than aluminum alloys. These propellers may have a protective coating other than paint. A possible coating may be polyurethane. These coatings may range in thickness from a few thousandths of an inch to many tens of thousands. Polyurethane is a well known material also used to protect hardwood floors in homes.
To maintain the propellers, the damaged protective film first needs to be removed. This removal presents a formidable practical problem. Conventional methods such as sanding, media blasting, scrapping or chiseling are both time consuming and may cause further damage to the underlying composite substrate therefore requiring further time consuming and expensive substrate repair after the old protective film is removed. FIG. 1 illustrates an approach to remove a protective film such as paint on metal such as a painted propeller. In this approach, the film is slowly ablated by decomposing the film in multiple passes of a scanned laser beam of appropriate optical characteristics. Typically, this approach also requires much power.